The present invention relates in general to an improved pumping system for use with liquid delivery vehicles. More particularly, the system of the present invention is a hydraulic system preferably for use with cryogenic liquid delivery vehicles.
Because it is dangerous to have hydrocarbons in proximity to the liquid cryogenic pump the cryogenic pump is usually disposed at the rear of the delivery vehicle or trailer and is separated a substantial distance from a drive for the cryogenic pump such as an internal combustion engine. In many cases the liquid cryogenic that is being delivered is oxygen which is dangerous when in proximity to the hydrocarbons commonly present about an internal combustion engine. Some prior systems provide a mechanical coupling that must extend a substantial distance between the internal combustion engine and the cryogenic pump. This internal combustion engine may be the engine powering the vehicle or may be a separate engine. This relatively long mechanical coupling arrangement is undesirable requiring excessive maintenance characterized by other operating problems. Another prior art technique is to use an extremely large alternator driven from the vehicle engine. This arrangement has also been found to be inefficient and troublesome.
Accordingly, one object of the present invention is to provide an improved pumping system for use on a liquid delivery vehicle for pumping preferably cryogenic liquids.
Another object of the present invention is to provide a hydraulic or a hydrostatic pumping system. In accordance with the invention for use with a trailer truck a separate internal combustion engine is used to drive a variable displacement hydrostatic transmission which in turn drives a liquid cryogenic delivery pump. The components of the hydrostatic transmission comprise a hydraulic pump coupled by hydraulic lines to a high speed hydraulic motor which is directly coupled to the cryogenic pump.
A further object of the present invention is to provide a cryogenic pump system that is safe in operation and rugged in construction and overcomes many of the problems associated with prior mechanical coupling systems.
Still another object of the present invention is to provide a cryogenic pump system that is readily adaptable for use with either smaller trucks or semi-trailer trucks or larger trailer trucks.
Still a further object of the present invention is to provide a pumping system that requires a minimum amount of maintenance especially in comparison with prior art systems.
Another object of the present invention is to provide a hydraulic pumping system preferably for use with cryogenic liquids and characterized by a maximum horse power that is available over a broad range of delivery pump speeds. With the system of this invention there is an optimization of the power and economy for the various delivery conditions that may be encountered.
Still a further object of the present invention is to provide a hydraulic system that is of the closed loop type. The closed loop system of the present invention requires a relatively small reserve reservoir tank and also eliminates the need for auxiliary valves which are usually necessary in an open loop system.